Catalytic isomerisation of α-pinene oxide in the presence of ETS-10 supported ferrocenium ions

• A hybrid material comprising ETS-10 and ferrocenium ions ([Fc]+) is described.
• Immobilisation of [Fc]+ was achieved by ion exchange under hydrothermal conditions.
• ETS-10/[Fc]+ displays catalytic activity for the isomerisation of α-pinene oxide.
• Under mild conditions, campholenic aldehyde (CPA) is obtained in up to 38% yield.
• ETS-10/[Fc]+ is stable toward leaching of iron-containing active species.

Ferrocenium ions, [Fc]+, have been immobilised in the microporous titanosilicate ETS-10 by ion exchange of Na+/K+ ions under hydrothermal conditions. The resultant hybrid inorganic-organometallic (ETS-10/[Fc]+) material was characterised by elemental analysis, diffuse reflectance UV–Vis spectroscopy, FT-IR spectroscopy, powder X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The ETS-10/[Fc]+ sample was tested as a catalyst for the isomerisation of α-pinene oxide (PinOx) at 35 °C. With α,α,α-trifluorotoluene (TFT) as solvent, campholenic aldehyde (CPA) was the main product formed in 38% yield at 100% conversion and 30 min reaction. Other reaction products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The same PinOx conversion and CPA yield could be reached within 1 min reaction time by increasing the reaction temperature (to 55 °C) and the Fe:PinOx molar ratio. Other solvents (hexane, CH3CN, toluene) led to poorer results than TFT. Characterisation of the used catalyst, together with an analysis of the catalytic activity of the liquid phase obtained after contact of ETS-10/[Fc]+ with TFT, indicated that the ETS-10/[Fc]+ sample was resistant toward leaching of iron-containing active species. When the recovered solid was reused in a second batch run, catalytic activity was lower than in the first run, while selectivity to CPA was higher.

A hybrid inorganic-organometallic (ETS-10/[Fc]+) material has been prepared, characterised, and tested as a catalyst for the isomerisation of α-pinene oxide. With α,α,α-trifluorotoluene as solvent, campholenic aldehyde was the main product formed in 38% yield at 100% conversion. The ETS-10/[Fc]+ hybrid material is resistant toward leaching of iron-containing active species.Figure optionsDownload as PowerPoint slide